1. Field of the Invention
This invention generally relates to a semisubmersible system for collecting a useful component present in sea water as dissolved therein, and, in particular, to a system for collecting a metal dissolved in sea water utilizing wave motion. More specifically, the present invention relates to a system for collecting a rare metal, such as uranium, which is dissolved in sea water.
2. Description of the Prior Art
Various useful components are dissolved in seawater, and rare metals, such as uranium, are also present in sea water as dissolved therein. However, since the concentration of any of such useful components present in sea water is so small, an enormous amount of sea water must be processed to collect such useful components from sea water. Besides, in order to make such a collecting operation economically feasible, use must be made of natural energy, such as tidal energy or wave energy. There has been proposed a system for collecting useful components from sea water utilizing wave motion as disclosed in the Japanese patent application No. 59-165525 (Patent Laid-Open Pub. No. 61-42392). According to this Application No. 59-165525, an adsorption unit including an adsorption chamber porous at top and bottom and containing therein a quantity of adsorbent is mounted at the bottom of a ship, whereby sea water moves through the adsorption chamber periodically and useful components present in the sea water are collected by the adsorbent.
In this case, the relative motion between the adsorption chamber and the sea water caused by wave motion is relied upon. However, since the adsorption unit is mounted at the bottom of a ship which floats at the sea surface, the adsorption unit tends to move up and down in phase with wave motion, so that the relative motion between the adsorption chamber and the sea water tends to be reduced. That is, the structure disclosed in the above-identified patent application No. 59-165525 is not efficient in utilization of wave motion in producing a relative motion between the adsorbent contained in the adsorption chamber and the sea water. It is important for sea water to pass through the adsorption chamber efficiently in order to obtain an enhanced collection efficiency of useful components, such as uranium, from sea water.